In postage meters, the franking head essentially comprises a rotary print head having print elements that are adjustable to different franking values, and metering means for monetary values, and in particular for the franked postal charges. In relatively large postage meters, the franking head constitutes a portable module which is removably mounted on a stationary base of the machine. Such machines use a conveyor to carry items of mail to be franked to the franking head. The conveyor itself is fed from a storage magazine for such items and fitted with an unstacker, or else is coupled to an automatic mail processing installation for putting mail into envelopes.
The conveyor is carried by the stationary base, with the franking head being mounted on the base at the end of the conveyor. Drive means are housed inside the stationary base and are coupled to the conveyor and to the franking head to drive them appropriately at the desired rate.
By making it possible to remove the franking head, it is possible, where necessary, to transport the franking head on its own. This is done, in particular, for operations relating to the monetary values recorded in the metering means, with such operations taking place off the premises of the user.
In order to ensure that the removable franking head is correctly mounted, the head and its stationary base are fitted with complementary means for positioning the head on the base. Manually controlled locking means are associated therewith. They enable the head to be locked in position for normal operation of the machine and for the head to be unlocked for removal purposes.
These complementary means for positioning the head on the base are constituted, for example, by a set of fingers projecting beneath the said head and by a corresponding set of holes in a platform of the base, at the end of the conveyor. These fingers projecting from the head act as legs for the head to stand on when it is removed from the base. There are therefore at least three fingers. The associated locking means are then constituted, for example, by a mechanism mounted inside the base beneath the platform and coupled to the external manual control, with grooves being provided in the fingers for engaging this mechanism. When the mechanism is engaged in the grooves, then the fingers are locked and cannot be withdrawn from the holes. In contrast, when the mechanism is disengaged from the grooves, the fingers are released and may be withdrawn from the holes in the platform.
In addition, such a postage meter having a removable franking head is provided with two complementary connector portions: one on the head and the other on the base, thereby enabling electrical signals to be interchanged between the head and the base when the connector portions are interconnected. In current machines, these connector portions plug into each other when the head is put into position on the base. The connector portions are often damaged by a head being incorrectly presented to the base. There is thus a risk of damaging the connector portions whenever the head is presented at an angle relative to the base, even though such an angle may make it easier to insert the positioning fingers into their holes in the platform of the base. Once the connector portions are damaged they need to be replaced and this has the consequence of making the postage meter unavailable for use in the meanwhile.
The object of the present invention is to reduce these risks.